Flotation processes have been used for some time in the coal industry to recover coal fines from previously discarded aqueous streams generated by processing raw coal. Generally, the flotation feed in a coal preparation plant comes from the fines and clays being washed away from the coarse fraction of coal which has been processed through dewatering screens, sieve bins, classifier tanks and hydrocyclones. The feed is normally 28 .times. 0 mesh and contains 4 to 12% solids.
The flotation circuit consists of four to eight cells in a single bank with the number of banks proportional to the total tonnage to be processed. The concentrate produced in the flotation cells goes to a vacuum filter where it is concentrated to approximately 75 to 80% solids. The tailings from the flotation process are discharged to a waste pond or a refuse vacuum filter. During the flotation process, the very fine clay that is in the circuit often becomes entrapped in the coal being floated and increases the amount of ash in the final product.
Accordingly, it is an object of this invention to improve the operation of the coal flotation circuit by improving the overall yield of coal.
It is another object of this invention to improve the operation of the coal flotation circuit by decreasing the ash content of the coal.
These and other objects of this invention are accomplished by the addition of cationic water soluble polymers to coal flotation circuits.